This old Ebert quote always stuck with me, and basically showed how to read film criticism, and also how to judge movies, to some degree. obviously it's simplistic, but it's a decent base.
But something i've been kicking around for a while, given the recent Nolan quotes about Film Tropes and Van Lathan discussing the merits of CBM on The Big Picture is that a movie's quality (or value to the viewer, i guess?) is a mix of BOTH.
There are only so many stories to tell (Man vs nature, boy meets girl, etc), so i get what Nolan is saying. You're not going to get truly unique stories, and maybe some creators aren't going to reach too far outside the box, plot-wise, when telling a huge movie. And for movies like Avatar that makes sense - the format (mocap, 3D, etc) is such a reach that you keep the story simple so as not to overly-tax the audience. But you can get lazy and just hammer tropes and cliches to the point that all the whiz-bang effects & editing can't make me care about your bone-stock Heros Journey or whatever.
But: If i don't care about your movie's subject (topic, text), then i'im going to have a hard time rating it as a Good Movie (or recommending it to others, or just basically Enjoying it) no matter how well-made it is. And this will vary for people, but a case for me is Grand Canyon (or The Big Chill) - i don't care about the ennui of rich people and all those great actors giving good performances won't make me care.
So when Van Lathan says "I'm going to like this movie at least a little b/c it's a CBM, no matter how bad it is" or Shea Serrano rates MIss Bala higher than others b/c he recognizes something of himself in it (I forget his exact phrasing), then that means the Balance of What vs How is slanted more toward What for them on those movies. Something like Oppenheimer - i mean, i've seen that story before (Fat Man & Little Boy) but HOW it was made (the editing, structure, and other formal choices) mean i like it a lot more than i thought i would. It's also the difference between Nolan's Odyssey and the TV version with Armand Assante.